In contrast with other NLP tasks, only few and limited evaluation challenges have been carried out for terminology acquisition. It is nevertheless important to assess the progress made, the quality and limitations of terminological tools. This paper argues that it is possible to define evaluation protocols for tasks as complex as computational terminology. We focus on the core task of term extraction for which we propose evaluation metrics. We take into account the specificity of computational terminology, the complexity of its outputs, the application, the user's role and the absence of well-established gold standard.